Manufacture of transparent sheets from musa fiber



Patented July 17, 1934 MANUFACTURE OF TRANSPARENT SHEETS FRoM -MUSA FIBER Edward Chauncey Worden, 1st, Millburn'Township, Essex County, N. 1., assignor to Hanson & Orth, New'York, N. Y., a firm composed of Charles D; Orth, Sr., Charles D. 0rth,'Jr., and

"Michael J. Smith No Drawing. Application August 2, 1930; I Serial No. 472,751 I I 1 Claim. (01. 18-57) I I I I that film, it follows that a film with the mini This invention is related to my co-pending application, Serial No. 421,069 .filed January 15th, 1930 for Manufacture of viscose rayon from Musa fiber cellulose which in turn; is related toapplication of Serial No. 347,457, filed March 15th, 1929 for Manufacture of rayon from hempfiberfiand is related to my 00- pending application, Serial No. 347,728, filed March 16th, 1929 for Manufacture of cellulose material from hemp fiber from which latter application, a continuation-in-part' beingSerial No. 356,890, filed March 20th 1929, has been made. a I One of the objects ofthis invention is to prepare film, sheets and plates in indefinite. length and considerable width, and of varying thickness in the finished product, which are transparent, fiexible and unusually high tensile strength both in the wet and dry state, by utilizing as the source of cellulose, the. highly purified alphacellulose obtained from Musa fiber as set forth in .Serial No... 356,890,. filed April 20th 1929, and converting the same into a xanthated product as set forth in my Serial No. 421,069 referred to above, from which cellulose xanthate prepared from Musa fiber alpha-cellulose, exceedingly tough, flexible and transparent sheets are obtainable when carrying out the process as forming the subject matter of this invention.

On account of the increased tensile strength of the regenerated cellulose, both in the dry and wet state, and the marked augmentation in stretch, elasticity and resiliency, when transformed from Musa alpha-cellulose into alkalicellulose; then the alkali-cellulose aged at the prescribed temperature for the correct number of hours; then transformed into a xanthated ester of cellulose with carbon bisulfide; then placed in solution by means of intimate mixture with aqueous sodium hydroxide solution to a pre-determinedalkalinity; then ripened or matured to-a determinable degree of maturity governed by analytical control; then cast into film, plate or sheet form by ways now known, results in the formation of a transparent film of desirable physical characteristics for the purposes to which intended, and by virtue of this augmentation in strength, elasticity, etc., forms a film which can be used in the trade of greater tenuity and less thickness than similar products desired viscosity,

mum thickness, is more supple and flexible by. virtue of the; diminished mass in a given area of saidfilm. With transparent sheets produced by my process from Musa fiber alpha-cellulose, and esterified into viscose and de-esterifiedas set forth in an illustrative process heretofore referred to, the increasedstrength of the-film; over other analogousproducts from arviscose base, admits of a smaller weight being used to cover a given'surface area With thesame .pro-- tective qualities. I

.The viscose solution, properly aged, of the instead of being projected through multi-orifice spinnerets as setforth in Ser. No. 421,069 for the production of filaments or rayon therefrom, may be treated in several methods as exemplifying my invention, one ;of which, given for illustrative purposes o lmbeing as follows:- r I The viscose solution, containing the equivalent of about seven percent of cellulose, butin. solu: tion in the Xanthate stage by virtue of the percentage of free sodium hydroxide associated therewith, and of a degree of ripeness or maturity represented by 8.0 cc. to 8.2 cc. by the acetic acid coagulation test, is placed in a storage tank, preferably glass lined, and vacuum applied thereto for several hours in order to remove therefrom, atmospheric air dissolved therein. The clarity of the solution has been previously brought to the desired standard by means of a series of filtrations similar to that used in the viscose rayon art and heretofore detailed.

The clarified, properly aged solution, freed from air or substantially so, is then forced under pressure (thedegree of pressure employed varying with the viscosity of the viscose solution employed) at a pressure from pounds to 90 pounds, through the slip in a hopper, which slit can be accurately adjusted as to diameter of aperture by means of a society screw arrangement, similar to that found on a compound microscope, the solution being projected through the hopper aperture or slit upward into a coagulating. or precipitating bath comprising the usual mixture of sulfuric acid, sodium sulfate or sodium sulfate and other alkali metal sulfate of composition and concentration which will decompose the viscose by neutralization of the alkali contained therein by virtue of the" acidity of the precipitating bath, thereby decomposing or de-esterifying the viscose solution, forming free sulfur, regenerated cellulose or hydrated cellulose and other removable complex bodies whose composition is little known and imperfectly understood.

The milky colored film, comprising elemental sulfur on and in the regenerated cellulose sheet, pellicle or plate, is passed through a bath of water to remove the products of decomposition in and on the film and to complete the coagulation of the viscose to the cellulose hydrate (hydrated cellulose) stage. The substantially neutral film is next fed into a desulfurizing solution of the normal type whereby the milkiness of the film is removed and transparency obtained by virtue of the dissolving effect or the desulfurizing solution upon the sulfur on and in said regenerated cellulose substance. The strength of the desulfurizing bath is that normally used in the viscose rayon industry, and the temperature of the bath maintained preferably within the range 40-60 C.

If it is desired to increase the flexibility, softness and suppleness of the film, after the products of reaction of the desuliurizing operation have been removed by an appropriate washing treatment, the film (still in sheet form) is immersed in a solution of glycol (or other suitable polyhydric aliphatic alcoholic body) passed through squeegee rollers to remove excess of softener, then over and through steam heated rolls until the film is substantially dry, after which it is rolled up and the process is complete.

It is usually unnecessary to bleach the transparent film (known in the trade as Musaphane) on account of the fact that a peculiarity of alpha-cellulose from Musa fiber is that in the normal process of treatment the color of film produced is normally as light as that obtained from normally bleached wood pulp or cotton pulp as used for viscose production in the rayon industry.

Transparent film may be produced from viscose in which the initial cellulosic material is 100% Musa alpha-cellulose, or mixtures of Musa-alphacellulose, with wood pulp or cotton pulp, as used in the rayon industry may be employed. Excellent results have been obtained for transparent film formation in indeterminate lengths by the employment as initial cellulosic material, of a mixture of 20%-30% Musa alphacellulose and 80%-70% purified wood pulp of high alphacellulose content. With increment in wood pulp and corresponding reduction in the percentage of Musa alphacellulose used as the starting oellulosic material, the less approaching true white is the color of the completed film, and.

the lower is the tensile strength both in the dry and wet stage, including the elasticity or stretch, and with increase in wood pulp, the more closely does the process in manufacture approach the manufacturing steps for viscose production asused at the present time in the viscose rayon industry.

Having now described my process and in what manner it may be performed, what I claim as new and desire to secure by Letters Patent is:

A process for the manufacture of transparent sheets, comprising treating purified Musa alphacellulose with sodium hydroxide to convert it to Musa alkali-cellulose, xanthating the alkali-eel lulose with carbon bisulphide, dissolving the Xanthated Musa cellulose in aqueous sodium hydroxide solution to form viscose having an alkalinity of 6.5% to 7% and a cellulose content of 6% to 6.5%, ripening theviscose to a maturity indicated in the acetic acid coagulation tests by 8 cc. to 8.2 cc. of 10% acetic acid, forcing the viscose in a purified state and after vacuum treatment through a slit of predetermined width under to 90 pounds per square inch pressure into an acid setting bath, and washing the resulting ing the same.

EDWARD CHAUNCEY WORDEN, I. 

